Determination of Sensitivity Versus Frequency Characteristics of Miniature Ultrasonic Hydrophones Below 1 MHz Using Planar Scanning Technique

OBJECTIVE: To develop and optimize a rapid and reliable ultrasonic hydrophone calibration procedure suitable for use in the frequency range from 100 to 1000 kHz. METHODS: Planar scanning technique was developed to determine the low-frequency response (<1 MHz) of an ultrasonic polyvinylidene difluoride membrane hydrophone probe. RESULTS: The frequency response of a bilaminar membrane design is presented in terms of end-of-cable voltage sensitivity versus frequency from 0.3 to 1 MHz and compared with the sensitivity data determined by other calibration techniques. The experimental data indicate that the sensitivity variation of the hydrophone determined by using the planar scanning technique is approximately +/-1 dB, which agrees well with that obtained using independent calibration methods. CONCLUSIONS: The planar scanning technique is suitable for absolute calibration of hydrophone probes in the frequency range below 1 MHz to within +/-1 dB. Also, the approach developed offers an alternative to other primary calibration techniques such as the reciprocity or broadband pulse technique. The results of this work are important for correctly determining the mechanical index, which is widely accepted as a predictor of potential bioeffects.